Police officers make decisions at the street level in a variety of situations that have direct impact on quality of life, justice in society, and individual freedom. These decisions inherently involve the exercise of discretion, since successfully performed police tasks are linked to the officer‘s choosing among alternative courses of action. Appropriateness of unsupervised decisions taken under street contingencies remains questionable in terms of police-behavior legitimacy. Law enforcement agencies seek ways to control excessive discretion to avoid undesired consequences of police discretion and maintain organizational legitimacy. Traditionally, organizations developed reward and sanction structures that aimed to shape officer behavior on the street. Recent perspectives, on the other hand, emphasize that it is imperative to manage discretion by employing a value-based approach that requires the agency to encourage subordinates in the exercise of certain behaviors simply because they are believed to be right and proper. This approach depends primarily on beliefs, values, and attitudes of employees rather than external contingencies of environment. Drawing on expectancy and value-based approaches, this study examines the factors affecting patrol officers‘ discretionary decisions to enforce law in the Turkish National Police (TNP). The reward expectancy concept was derived from the expectancy theory of motivation, which uses extrinsic rewards in structuring discretion. Regarding the value-based approach, public service motivation (PSM) represents the intrinsic motives of officers in this study, while selective enforcement corresponds to the attitudes of officers. Discretionary behaviors of officers on the street were conceptualized as responsiveness, which refers to the degree to which officers iv are willing to respond to street contingencies. The study tested the mediating role of work effort between reward expectancy/responsiveness and public service motivation/responsiveness relationships. Samples of the study were drawn from uniformed patrol officers in seven provinces of Turkey. A self-administered questionnaire was used to collect data. Responses of 613 patrol officers were analyzed using structural equation modeling (SEM). The study developed four latent constructs and validated their measurement models by using confirmatory factor analysis (CFA). Structural equation modeling was used to investigate causal and confirmatory relationships among latent variables. Findings of the study suggested that reward expectancy did not have a statistically significant relationship to responsiveness. The study did not find a significant association between reward expectancy and work effort of officers. This finding was found to be attributable to the fact that officers do not believe in the fair distribution procedures of rewards and they do not value organizational rewards. Public service motivation of respondents, on the other hand, indicated a strong, positive, and statistically significant relationship with both work effort and responsiveness. These results indicated that intrinsic motives of officers in the TNP are more powerful in explaining officer responsiveness to street contingencies. As hypothesized, officer attitudes toward selective enforcement negatively influenced officer responsiveness, indicating that officers‘ beliefs and values influence their discretionary behaviors. Among the demographic characteristics of participants, only age of officer indicated a negative significant relationship to responsiveness. This finding suggested that motivation decreases as age increases. Contrary to v other findings in the literature, this study found that intensity perceptions of respondents was positively associated with responsiveness. The study revealed some policy, theoretical, and methodological implications. The findings suggested that the TNP should either completely eliminate the existing reward system or revise it to motivate officers to be responsive. A leadership practice that promotes PSM and discourages selective enforcement was also suggested. Contrary to research that emphasizes the role of extrinsic motivation on police discretion, this study empirically reported that intrinsic motivation has an even stronger effect on officer behavior and needs to be taken into account in future studies. The study contributes to an understanding of police discretionary behavior in the TNP, which has unique characteristics of structure, culture, and law. The limitations of the study in terms of its dependency on officer perceptions and concerns about construct validity were discussed and future research was suggested.